This application is related to the following pending applications being concurrently filed herewith and assigned to the assignee of the present invention:
This invention relates generally to air conditioning systems and, more particularly, to an air conditioning system for the rooftop of a bus.
The most common approach for air conditioning a bus is to locate the air conditioning components on the rooftop thereof. Inasmuch as power is available from the engine that drives the bus, it has become common practice to locate the air conditioning compressor near the drive engine such that the drive engine is drivingly connected to the compressor, with the compressor then being fluidly interconnected to the air conditioning system on a rooftop of a bus. This, of course, requires rather extensive piping between the engine compartment and the air conditioning unit, thereby increasing installation and maintenance costs.
Another problem with such existing systems is that the speed that the compressor is driven is dependent on the speed in which the drive engine is running. Thus, when the drive engine is idling in a parking lot, for example, the compressor is running at a relatively slow speed which may not be sufficient to provide the desired degree of air conditioning. It is therefore generally necessary to oversize the compressor in order to obtain the performance needed under these conditions.
Others problems associated with such a motor driven compressor system is that the open drive compressor needs a shaft seal and a mechanical clutch, both of which are subject to maintenance problems. Further, since DC power is available on a bus, DC motors have been used for the air conditioning system. In general, DC motors are not as reliable as AC motors since they have brushes that wear out, and brushless motors are relatively expensive.
In addition to the problems discussed hereinabove, it is recognized, that because the wide variety of bus types and application requirements, it has been necessary to provide many different types and variations of air conditioning systems in order to meet these different requirements and vehicle interfaces. As a result, the manufacturing and installation costs, and sustaining engineering resources that are necessary in order to properly maintain and service these units, are relatively high.
Also associated with the existing bus air conditioning systems is the problem of a component failure causing a complete loss of the air conditioning capacity. That is, with a single large unit as is now customary, failure of that unit such as, for example, a leaking hose causing loss of refrigerant, an electrical failure leading to inoperation of one of the components such as a fan, or a compressor failure, the entire unit is inoperable and no air conditioning can be provided to the unit. In such a situation, it would preferable if partial capacity could be maintained in order to provide a xe2x80x9climp homexe2x80x9d capability.
It is therefore an object of the present invention to provide an improved bus top air conditioning system.
Another object of the present invention is the provision for a bus air conditioning system which is effective at all operating engine speeds of the bus, while at the same time does not require an oversized compressor.
Yet another object of the present invention is the provision for reducing the manufacturing, installation, and maintenance costs of a bus air conditioning system.
Another object of the present invention is that of providing a xe2x80x9climp homexe2x80x9d capability in the event of certain component failures.
Yet another object of the present invention is the provision for a bus rooftop air conditioning system which is economical to manufacture and effective in use.
These objects and other features and advantages become more readily apparent upon reference to the following descriptions when taken in conjunction with the appended drawings.
Briefly, in accordance with one aspect of the invention, an air conditioning module is assembled with its condenser coil, evaporator coil and respective blowers located within the module and so situated that a standard module can accommodate various installation interfaces with different types and locations of return air and supply air ducts on a bus.
In accordance with another aspect of the invention, rather than a large single air conditioning unit, a plurality of relatively small identical modules can be installed on the roof of a bus, with each being capable of operating independently of the others so as to allow for the relatively low cost mass production of identical standardized units and also provide for a limp home capability in the event of failure of one or more units.
In accordance with another aspect of the invention, each of a plurality of modules are installed in a centered relationship with respect to a longitudinal centerline of the bus and extend transversely across the width of the bus. The number and length of modules is dependent on the total air conditioning capacity requirement of the bus.
By yet another aspect of the invention, each of the identical modules includes all the necessary components with electrical power being provided to the electrical components by an inverter/controller that is powered by an engine driven generator.
By another aspect of the invention provision is made for mounting the frames of multiple modules in adjacent or longitudinally spaced positions on the bus rooftop by way of a pair of longitudinally extending rails.
By still another aspect of the invention the evaporator section of the modules has a return air compartment that spans a substantial width of the bus to thereby accommodate various sizes and types of return air interface requirements.
By yet another aspect of the invention the evaporator section of each module has three different vertical levels to accommodate the respective incoming flows of return air and replenishing fresh air, and includes a mixer for selectively varying the amount of each which passes to the fan and then to the evaporator coil.
In the drawings as hereinafter described, a preferred embodiment is depicted; however various other modifications and alternate constructions can be made thereto without departing from the true spirit and scope of the invention.